Oscillograph control circuit



April 12, 1949. c. l. BRADFORD ETAL 2,466,924

OSCILLOGRAPH CONTROL CIRCUIT Filed May 18, 1945 2 Sheets-Sheet i I l v @Q 1a I l //3 7 /07-* i /27 /08 i I /22 i f/Za i1 v /5' W1 INVENTORS C OL-lN/RV/NG Brnaroza PHI/L f7 Pamsy BY h ATTORNEKS April 12, 19 49. c. l. BRADFORD ETAL 2,466,924

OSCILLOGRAPH CONTROL CIRCUIT Filed May 1.8, 1945 2 Sheets-Sheet 2 I l i l 1/0 /46 1 INVENTOR PA L f Dams) BY AT ORNEYJ Patented Apr. 12, 1949 OSCILLOGRAPH CONTROL CIRCUIT Colin Irving Bradford and Paul F. Darby, Fairfield, Conn., assignors to Remington Arms Company, Inc., Bridgeport, Conn, a corporation of Delaware Application May 18, 1945, Serial No. 594,560 (01. 315-22) 3 Claims. 1

This invention relates to cathode ray oscillographs and particularly to an instrument suitable for investigating transient or periodic phenomena such as found in research work in the arms and ammunition field. An example of such investigation is the determination of the shape of the pressure curve as a gun is fired.

The invention has as one of its objects to provide an instrument which will be flexible and suitable for various combinations of use and to contain the desirable features for employment in investigating problems in the arms and ammunition field. One of these requirements is the provision of a means for simultaneouslyturning on a cathode ray tube spot and initiating the sweep thereof and then extinguishing the spot and stopping the sweep at the end of a predetermined interval. It is also desirable to provide a calibrating circuit particularly adaptable for use in the device. These and other objects will become apparent from the drawings and description which are to be considered merely as exemp ary.

In the drawings:

Fig. 1 is a'wiring diagram showing the vertical amplifier, sweep generator, horizontal amplifier, spot and sweep exciter, and calibration circuits.

Fig. 2 is an extension to the right of the wiring diagram of Fig. 1 and contains the cathode ray tube circuit, the high voltage supply circuit, the low voltage supply circuit, and the spot control and modulation circuits.

In the investigation of transient phenomena, such as pressure rise as a cartridge is fired, it is necessary to have extreme fidelity 'in the trace shown on the cathode ray screen because small difierences may be quite important in the subject under consideration. For this reason, the various circuits must be arranged carefully so as to obtain the desired results. The attenuator and amplifier stages must be such that the true wave form is transmitted through the circuit to the cathode ray tube. The oscillograph also should be arranged so that it may be used with an external synchronizing voltage on the spot and sweep control circuit or so that internal alternating current may be applied to said circuit. The spot and sweep exciter also is arranged so that the open ing or closing of an external circuit, such as the firing of a gun, will initiate the spot and sweep and cause it to persist for a predetermined time interval. The spot and sweep exciter is arranged so that the time interval is adjustable.

In general, the upper block ll0 enclosed in dotted lines in Fig. 1 is the vertical amplifier circuit for the vertical plates of the cathode ray tube. The circuit enclosed in dotted lines I l-ll comprises the sweep generator and horizontal amplifier. The dotted lines l2l2 enclose the spot and sweep exciter circuit and switching apparatus therefor. The dotted lines |3-I3 enclose the calibration circuit.

In Fig. 2, dotted lines [4-44, is seen the oathode ray tube circuit including spot positioning, intensity, and focusing controls. Dotted lines I5l5 include the high voltage supply circuit which is a conventional voltage doubling arrangement. The block I6l6 includes the low voltage supply circuit which is a conventional arrangement having a full wave rectifier circuit, voltage regulator tubes, and a negative supply circuit. The block enclosed by dotted lines l'l-l'l includes the spot control and modulation circuit. The spot control is excited by the spot and sweep exciter in block l2-l2. Provisions are made in block lI-ll for superimposing an alternating current voltage on the control grid of the cathode ray tube so as to give an interrupted trace on the cathode ray tube screen. The circuits of the various blocks now will be described in order.

Vertical amplifier The vertical amplifier circuit for the vertical plates 20, 20 of cathode ray tube 2| is shown in block Ill-I0. An arrangement is provided for changing the gain of said amplifier circuit and for also changing the gain and connecting a condenser across the input circuit when it is desired to calibrate or investigate piezo electric crystal gauges such as those used in a pressure indicator as shown in the patent to Bradford, No. 2,350,545. The input for the vertical amplifier is connected across terminals 22 and 23. Tube 24 may be a pentode of the 6J7 type. It is to be understood that equivalent tubes may be used wherever a particular type is mentioned. The control grid 25 of said tube is selectively connected through switch 26' with various control means. Switch 26, 26 is a two-circuit switch having a lower portion 26' connected therewith. When switch 26, 26' is located on the third contact or 21, 21', the control grid 25 is connected to input terminal 22 directly through blocking condenser 3| and in this position the device has maximum gain and can be used when a low voltage input is employed. It is to be noted that the lower contact 21' is blank. When the switch 26, 26' is moved to the lowest set of contacts 28 and 28, the control grid 25 is connected to input terminal 22 through a voltage divider 3 comprising resistances 32 and 33, said control grid being connected at the midpoint between resistances 32 and 33. When in this position,

only part of the voltage applied to the amplifier will be used. If it is desired to connect variable condenser 34 across the input terminals for use with a piezo electric pressure gauge or similar device, the upper contacts of switch 26, 26' are used. When the switch is in position 29, 29,

the condenser 34 is connected across terminals 22 and 23 and the control grid is connected directly to the input. When it is desired to use less than the full voltage being applied and still have the condenser across the input circuit,

switch 26 is moved to the second position or in contact with points 30 and 30'.

Tube 24 has a cathode follower attenuator ar rangement with a resistance 31 between the cathode 36 of said tube and ground. Tube 35- has control grid 36 thereof connected through blocking condenser 31 to attenuator 38. Attenuator38 is in parallel with resistance 31 and connected thereto through condenser 39. In this manner, alternating current only is transmitted. to the next tube (35) and direct current is. blocked. Attenuator 38 is adjustable, and by this arrangement only the alternating current variation will be transmitted to tube 35 and none of the direct current component. Tube 35 may be a conventional pentode tube of any desired type such as a 6SJ'7. Tube 40 may be similar to tube. 35, these two tubes acting as conventional amplifiers. and being connected to thepush-pull amplifier circuit including tubes 4! and 42.

This is a conventional internal signal inverter push-pull amplifier. The signal is transmitted to control grid 43 of tube 4|. The cathode circuit of tube 4| contains a connection 44 to the cathode of tube 42. When tube 4| becomes conducting it becomes apparent that the grid potential on tube 42 will become more negative in pushpull arrangement. The output of the push-pull amplifier is connected to the vertical deflection plates 26, 26 of tube 2| throughleads' B--B. Lead A is the source of low voltage supply for operating the vertical amplifier circuit. The spot positioning means for the vertical amplifier is arranged in a conventional manner from potential divider 45 through lead C-C, resistance 46, to the control grid circuit of tube M. The other portions of this circuit are conventional and no description is needed thereof.

Sweep and horizontal amplifier The sweep and horizontal amplifier circuit is shown in block I l-I I. The sweep generator and horizontal amplifier circuit is started by the spot and sweep exciter which will be described at a later point, the input lead to start the sweep generator being connection 41. When it is desired to apply an externally genera-ted signal to the amplifier switch 50 is close to the left on contact 50". When switch is at the right (as shown in Fig. 1') the bias on tube 52 is such that thesweep will operate continuously or periodically. In order to stop the sweep, switch 5| must be moved from its right hand position. When switch 5| is inits left hand position or the blades thereof touch contacts 53 and 54, lead 4-! from the spot and sweep exciter is connected through 53, the upper switch blade and lead 55 to the grid of gaseous discharge tube 52. The lower contact 54- connects the biasing circuit to ground. Tube 52 may be type 884 or equivalent. When switch 5| is in the right hand position so that the sweep is operating continuously, at synchronizing voltage may be applied through the spot and sweep exciter in a manner which will be described at a later point.

Tube 56 may be a type 6SJ7 constant current tube. Condenser 51 is the sweep generator condenser. This: condenser is charged from voltage regulator tube 58, lead 59, condenser 51 through tube 56. In order to limit the voltage applied so as to maintain linearity in the sweep, tube 50 may be connected across Voltage divider 6! so that point 62' cannot reach the full voltage applied across voltage regulator 58 and in this manner prevent sweep generator condenser 51 from obta-ining full voltage and thus provide for linearity. The voltage divider BI is connected across the voltage regulator tube 58 so that it becomes evident that tube 56 will be at a lower potential. Gondenser 51 is discharged through tube 52 when a signal is placed on the control grid of said tube.

The signal. for amplifier tube 63 is taken from condenserfll through lead 64, switch 50, lead 65, blocking condenser: 66-. The switch 50' is thrown to the rightfor this operation. Tube 63 has a cathode follower attenuator arrangement generally similar to tube 24 in block 10-46. The bias for the control grid of tube 63 is taken through lead 61' and resistor network 68. Attenuator 69 is connected by lead 10 to the control grid of the push-pull amplifier tube H. Push-pull amplifier tube H and push-pull amplifier tube 72 are connected in the same manner as tubes 1H and 42' contained in the Vertical amplifier. The signal from the horizontal push-pull amplifier is. connected by leads E-E to the horizontal deflection plates 13-13 of the cathode ray tube. The horizontal spot positioning is accomplished by potentiometer 14 which i is connected through leads F-'-Fand resistance 15 to the control grid of push-pull amplifier tube H.

Spot and sweep emczter The spot and sweep exciter for the purpose of initiating the spot and sweep or for providing other combinations is shownin the block i2-l2. Switches 16' and 76' are an inter-connected twocircuit switch. The operation of this switch will be described for each position in order. When the switch blades are in their upper positions or with the blades on contacts I! and 11', an impulse placed across input terminals 8 I and 82 will cause gaseous discharge tube 83 to trip. The action of this tube will be described at a later point as will the s'pecificarrang'ement for utilizing the trip impulse. The signal from the spot and sweep exoiter is transmitted to the sweep generator through lead 41, which, in turn, is connected to the switch blade of switch '16". It is seen that 11" is blank so that no signal is applied to the sweep generator in this position. The spot, however, is turned on through lead J-J to the spot control circuit shown within dotted lines 11-41 (Fig. 2). When the" switch is placed in the second position or when the blades contact 18 and 78', the impulse placed across input terminals 8| and 82 trips tube 83 and starts the spot, as just described. The signal is also transmitted through lead 84, switch contact l8, lead 41, to the sweep generator to start the same in operation. In other. words, in the second position of the switch both the spot and the sweep are initiated simultaneously. When the switch: l6, 16 is moved to thethird position or where the blades are in contact with 79; 16 a synchronizing voltage maybe applied from an external source through input connections SI and 82, through the switch blade of I6, contact I9, condenser 85, potentiometer 86, contact 19, lead 41, to the sweep generator. This provides continuous operation of the sweep generator. For this operation, the spot is turned on manually by the potentiometer 81 (Fig. 2) in a manner which will be described in conjunction with the description of the spot control and modulation circuit. When the switch I6 and I8 is placed in its fourth or lower position so that the blades are in contact with 80 and 80, internal alternating current of the oscillograph is applied to the sweep generator for synchronization of a continuous sweep. This voltage is applied from a filament transformer winding 88 (Fig. 2) to condenser 89 through contact 80', switch blade of IS, lead 41, to the sweep generator.

The arrangement for utilizing a make or break contact source applied to input connections 8!, 82 now will be described. When an external contact is made across the input connections 8I and 82 or an external positive voltage pulse is applied, switch 90 is left in its open position. Then, with switch I6, I6 having been placed in one of its upper two positions, the signal is transmitted through 8|, switch blade of I8, contact 11 or 18. to the control grid 9I of the gaseous discharge tube 83, which will trip the tube by raising the grid potential thereof. If it is desired to open a contact in the provision of a signal to the spot and sweep exciter, switch 90 is closed. When switch 90 is closed, a positive source is provided across terminals 8| and 82, which is shortcircuited by the external connection. When the external connection or switch is opened, a positive signal is placed on the grid of tube 83 to cause said tube to trip. When gaseous discharge tube 83 is fired, the cathode follower signal circuit applies a signal to the control grid 92 of gaseous discharge tube 93. This serves to cause a flow in the plate circuit of said tube from lead G, resistance 94, plate 95, cathode 96 to ground through signal resistances 91 and 98, (Fig. 2). When tube 93 becomes conducting, variable condenser 99 will start charging in the direction shown. When condenser 99 has a sufficiently positive charge on the upper plate thereof, control grid I of gaseous discharge tube IOI will become suificiently positive to trip tube IOI. Condenser I02 has been previously charged from lead G, point I03, the condenser, resistance I04, to ground I05. When tube IOI becomes conducting, condenser I02 discharges through resistance 94 and through the tube IOI. The additional flow of current through resistance 94 will depress the potential at point I06 sufliciently to reduce the potential on the anode 95 of tube 93 so that tube 93 will extinguish itself. After condenser I02 has discharged, tube IOI again becomes non-conducting and the control grid regains control, thereby automatically resetting the circuit. The signal, which is of a square wave type, is taken for sweep generator through lead 84, as previously described. The signal for the spot control to turn the spot on automatically is taken by lead J to the spot control apparatus in box III'I.

Calibration circuit The circuit for calibrating the instrument, is contained in box I3-I3. Terminals I01, I08 are the output terminals for the calibration circuit and these terminals may be connected, for example, to the input terminals for the vertical amplifier at 22, 23 or for the horizontal amplifier 48, 49. When the latter connection is used, the switch 50 is closed on contact 50' so that the amplifier circuit only is used. The calibrating circuit will first be described as a method of obtaining a positive square wave for calibrating purposes. Switch I09 is thrown to the right so that the switch blades make contact at H0 and III. Push button switch H2 is open, as shown. In this condition, gaseous discharge tube I I3 and gaseous discharge tube I I4 are in their non-conducting state. The switch in the spot and sweep exciter is closed so as to place a pulse on the spot and sweep exciter. This causes a pulse to appear on lead J, which starts the spot through the circuit enclosed in box II--II, which will be described hereafter. The signal is also led through wire H5, contact III, resistance H6, to the control grid of tube H3. Variable condenser H1 is connected between a point on the other side of resistance H8 and ground. Condenser HT is also mechanically connected to variable condenser 99 of the spot and sweep exciter. By this means, the capacities of the condensers are varied together. Condenser HI starts to charge and when the potential on control grid of tube H3 is raised sufiiciently high, tube H3 will fire. By this means, condenser HI supplies a delay before the square wave calibrating circuit becomes operative after the spot and sweep have become energized. The current fiow to tube H3 is through positive voltage supply lead K, wire H9, variable resistance I20, terminal I2I, external milliammeter I22, terminal I23, resistance I24, through .tube H3, and through the cathode resistor I25 to ground. The signal is taken from the cathode resistor by variable contact I26 to terminal I01. The voltage on lead H9 may be regulated by means of the gaseous regulator tube I2I. In order to extinguish tube H3, push-button H2 may be operated. Lead I28 supplies negative bias from the voltage supply to the grid of gaseous discharge tube H4. When the push button H2 is operated, the bias on tube H4 is made more positive so that tube H4 fires. Previous to this, condenser I29 has been charged through voltage supply lead H9. Firing of tube H4 will discharge condenser I29 through resistance I30. When this occurs, the additional voltage drop across resistance I30 will be sufilcient to depress the potential on anode I3I of tube H3 sufiiciently far to extinguish tube H3. Tube H I extinguishes itself upon the discharge of condenser I29, thus making this circuit automatically resetting.

In order to supply a negative square wave for calibration purposes, switch I09 is thrown to the left so that the switch blades are on contacts I32 and I33. Switch H2 is then closed so as to trip tube H3, the control grid of tube H3 having previously had negative bias placed thereon throughlead I28 and resistance H0. Tube H3 then becomes conducting. Then switch 90 may be closed so as to start the spot which will again provide a signal through lead J,.lead H5, resist ance H9, switch I09, contact I33, to the control grid of gaseous discharge tube H4, condenser HI again charges and when it has become sufficiently charged, the bias on tube H4 will be such as to cause this tube to trip, condenser I29 having previously become charged. The additional current through resistance I30 then will depress the potential on anode I3I of gaseous discharge tube H3 and cause conduction therethrough to stop. The change in the cathode cirsuit. from conducting; to. non-conducting willprovide. a. negative. square wave between terminals I 6"! and I08".

Variable: resistance; I? can; be changed so as to give the desired current flow through tube M3, external; meter I22 being available for determination ofthis currentfiow. Then, the adjust.- able tap I265 on cathode resistor I25may be'operated to givethe: desired voltageacross terminals I0 and 18;.

High voltage supply The. high voltage'supply is shown in box. I5.I.5 including two rectifier tubes, I32 and I33, which may be type37 9. Thetubes may be supplied from transformer I34- having a secondary to give about 4000 volts. The tubesare. connected. in voltage doubler arrangement so that lead I35" to the. intensifier plate I36 oi the cathode ray tube will be approximately plus2000 volts. LeadI3I (box I 5--I5, box I.I--I 1) is connected through lead resistance 38,. lead 136, up to point I43 (box [4-44) The cathode of tube 2] is supplied. from point M0- through resistance. MI, I42, lead'l'43, to cathode MILL The potential at point I40 is sub..- stantially minus 2000 volts. In this manner, there is a total potential of. 4000 volts supplied across tube 2]. Transformers I and H16 are filament transformers. for tubes I32 and H3 respectively.

Law voltage supply Low voltage supply circuit is shown inbox I6-I6 and is a conventional full wave rectifier circuit having rectifier tubes: I41 and I46 which may be type 81.. Tube Mills a halfwave rectifier to supplya negative bias for the various tubes of the circuit, said bias being supplied through wire I56 connected to lead I-I-H and L--L. Voltage regulator tubes I'5I' and I52 may be used for the purpose of regulating the voltage supplied, tube I52 regulating the negative supply and tube I51 regulating the positive supply. The positive leads comprise wires I53 and I54. The voltage supplied by lead I53, for example, can be approximately 600 volts and the voltage by lead I54 approximately 150 volts. There is a condenser filter network I55 of conventional design.

Spot control and. modulation The spot control and modulation device'is for the purpose of turning the spot on and ofi when a signal is'supplied by the spot. and sweep exciter. There is also provision to superimpose an alternating current on. the spot control so: as. to. give an interrupted trace. The positive signal from the spot and sweep exciter is carried by lead' J to point I56. Tube I5'I is an amplifier tube and may be a pentode type 6SJ7. Normal negative cut-01f bias is supplied to tube I5'I' from tube I49, lead I50, lead I60, resistance I59 to the control grid of tube I51 through the secondary of transformer I'I'I. As tube I5'I' becomes conducting due to a positive pulse carried by leadxJ the plate current flows from the ,voltage supply lead.- I54 (box I6-I6), lead I6I, lead I62, resistance I63, resistance I64, through tube I5'I'. The signal from the place circuit of tube I5'I is carried to the control grid I66 of amplifier tube I65 which may be a-pentode of the. 68K? type. As tube. I51 becomes more. conducting, the signal on the control grid I66 of tube I65 will be such as tov reduce: the con,- duction of I65. The. plate circuit of. I65 maybe traced from contactv 81 on resistance; I42, lead I6I', signal resistance I68, tube I65, point I69, lead I39; back to point I II1= so that a positive potential difference between apoint on-resistance 8'! and point Mllis: applied; across tube: I565; The. bias. on: the

control" grid I'Ill ofthecathode ray ttube; issupplied from point I12 through lead. I-II; to: thegrid I'I'II; Under: normal. conditionathe point I12 is more negativethan when tube. I65 has conduction reduced therethrough. When the conduction through I65 is reduced, point I'IZ- becomes more positive due to less how of current through: resistance I68, thereby causing control. grid? I-"I0- of the. cathode ray tubeto become more positive. Switch I13 is in the? upper position as shown when it. is desired to. set the intensity at the cathode ray tube. When the switch is inthe upper position, thenegativebias on tube I65 isincreased sufiiciently so as to turn. on the spot. When the device is ready foroperation, switch I 'l'3 isplaced in its lower position sothat reduced bias is on the tube I65, causing it to be moreconducting.

If it is desired to. provide an interrupted trace such as, for example; to put a time base directly on the trace, a source of alternating current may be connected to leads I'M, I15. This signal is appliedtoamplifier tube H6. The plate circuit of. tube I16 passes-through the primary of transformer I11 and the secondary of. transformer H1. is located in thegrid circuit for tube. I51. In this manner, alternating. current is superimposed onv the gridbias. for tube, I 51 so that during thenegativeimpulsesof. the modulating current,the trace willbeblanked out.

What is claimed is:

1. A pulse generator for producing square wave output of adjustable time duration. comprising a normally non-conducting grid. controlled gaseous tube having its cathode at a higher potential. when the tube is conducting than when the. tube is. non-conducting;v means to: apply an input signal. tothe grid of.,said tube to'render said tube: conducting; a. normally discharged condenser connected. between. said cathode and. a point of lower potential. to. be charged when said. tube is conducting; adjustable means to. vary. the RC time constant of the. charging. circuit. of said condenser; a second. normally non-conductinggrid. controlled, gaseous tube having its. grid. courpledthrough a coupling condenser to the cathode side of said normally discharged condenser; electrical circuit meansconnecting the plates of both said gaseous. tubes together; a single plate resistor connecting said. common. plate connection. to. a source. of positive potential; and. a normally charged condenser connected betweenthe cathode of said secondgaseous tube. andsaid sourceof positive-potential in shunt relation to. said. second tube whereby a square wave pulse of time duration controlled by said adjustable means. may betaken from the. plate cathode circuit of. said first tube when-said firsttube: is fired by a positive pulse applied to its grid, said second tube firing. when said normally discharged condenser has been sufficientl-y chargedtoovercome the biasof said second tube, the discharge. of said normally charged. condenser through said second tube immediately extinguishing said. first tubeby robbing itof plate voltage.- as a function of the. increased current through said single plate resistor andsubsequently extinguishing said second tube when thevolt age of said normally charged condenser falls be low that required to maintain ionization in said secondv tube.

2. In combination. with a cathode; ray- 0scil1ograph. the pulse; generator described inclaim 1, anelectronic. bias control circuit for said. oscillograph. constructed and arranged for normally biasing the oscillograph so that no spot appears thereon; electrical circuit means applying the pulse from said generator to said bias control air-- cuit to reverse the condition thereof so that a spot does appear on said oscillograph; a sweep voltage generator constructed and arranged to apply a spot deflecting voltage to said oscillograph; and electrical circuit means to apply the pulse from said generator as a synchronizing signal to initiate the action of said sweep voltage generator simultaneously with the turning on of said spot.

3. In combination with a cathode ray oscillograph the pulse generator described in claim 1, biasing means for the control grid of the cathode ray tube comprising a voltage divider, one portion of which is in parallel with the cathode to plate path through a vacuum tube, the control grid of said cathode ray tube being so connected to said voltage divider as to be biased negatively to cut off when said vacuum tube is non-conducting so that no spot appears on the screen of said cathode ray tube; electrical circuit means applying the pulse from said pulse generator to said vacuum tube to cause same to become conducting and decrease the negative bias on said cathode ray tube permitting a spot to appear thereon; a sweep volt- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number N arn-e Date 2,089,430 Roys et al Aug. 10, 1937 2,222,943 George Nov. 26, 1940 2,303,924 Faudell Dec. 1, 1942 2,315,848 Geohegan Apr. 6, 1943 2,360,857 Eldredge Oct. 24, 1944 2,363,810 Schrader et a1 Nov. 28, 1944 2,406,970 Smith 1- Sept. 3, 1946 2,415,870 De Ryder Feb. 18, 1947 2,431,766 Miller et al Dec. 2, 1947 

